Taboos and measures in forged steel valves pipeline construction-part three
Mar 18, 2019
Taboo 10: The flanges and gaskets of the pipe connections are not strong enough, and the connecting bolts are short or have a small diameter. Heat distribution pipelines use rubber gaskets, cold water pipes use asbestos gaskets, and double-layer gaskets or beveled gaskets with flange gasket protruding into the pipe.
Consequences: The flange connection is not tight, even damaged, and leakage occurs. The flange gasket protrudes into the tube and increases the flow resistance.
Measures: Flanges and gaskets for pipes must meet the pressure requirements for piping design. Rubber asbestos gaskets should be used for the flange gaskets of heating and hot water supply pipes; rubber gaskets should be used for the flange gaskets of water supply and drainage pipes. The gasket of the flange shall not protrude into the pipe. The outer circle of flange gasket is preferably to the bolt hole. No inclined gasket or several gaskets shall be placed in the middle of the flange. The bolt diameter of the connecting flange should be less than 2 mm than the flange diameter. The length of the bolt stem protruding nut should be 1/2 of the thickness of the nut.
Taboo 11: When conducting the hydraulic pressure test and tightness test of the pipeline system, only observe pressure values and water level changes, while carry out insufficient inspection of leaks,
Consequences: Leakage occurs after the pipeline system is in operation, affecting normal use.
Measures: When the pipeline system is tested according to the design requirements and construction specifications, in addition to recording the pressure value or water level change within the specified time, it is especially necessary to carefully check whether there is leakage.
Taboo 12: Sewage, rainwater, and condensate pipes are concealed without a closed water test.
Consequences: May cause water leakage and cause user losses.
Measures: The closed water test should be checked and accepted in strict accordance with the specifications. Concealed sewage, rainwater, condensate pipes, etc., buried underground, inside suspended ceilings, between pipelines, etc., must be ensured that they do not leak.
Taboo13: No flushing thoroughly before the completion of the piping system, and the flow rate and speed are not up to the pipeline flushing requirements. More terrible, water release after the water pressure test replaces flushing.
Consequences: Water quality does not meet the requirements for pipeline system operation, and often results in reduced or blocked pipe sections.
Measures: Flush with the maximum flow rate in the system or at a water flow rate of not less than 3 m/s. The water color and transparency of the discharge port should be consistent with the water color and transparency of the inlet water by visual inspection.
Taboo 14: The hydrostatic test is carried out at a negative temperature during winter construction.
Consequences: The tube freezes off quickly due to the rapid freezing of the tube water during the hydrostatic test.
Measures: Try to carry out the hydrostatic test before the winter application, and blow the water off after the pressure test, especially the water in the forged steel valve must be removed to the net, otherwise the forged steel valve will freeze. If the hydrostatic test must be carried out in a winter project, be sure that the test is carried out at a normal indoor temperature and the water must be blown off after the test. When the hydrostatic test is not possible, it can be tested with compressed air.
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